1. Field of the Invention
The present invention relates to a brake operation structure applied to a working vehicle including a friction-plate type brake mechanism, a transmission case that accommodates the brake mechanism, a driver's seat that is disposed above the transmission case, and a fender that covers a side of the driver's seat.
The present invention also related to a brake/differential-lock operation structure applied to a working vehicle including a friction-plate type brake mechanism and a differential mechanism capable of switching between a differential state and a differential-lock state.
2. Background Art
There is known a brake operation structure used for operating a friction-plate type brake mechanism that includes group of friction plates and a brake pressing member and is configured so that, in accordance with rotation of the brake pressing member about a rotational axis line into a brake actuation direction, the group of friction plates are brought into frictional contact with each other to operatively apply braking power to a drive axle. The brake operation structure is provided with a brake adjustment mechanism that is capable of adjusting an initial position of the brake pressing member around the rotational axis line at which the brake pressing member is positioned when the brake operating member is located at a brake release position (see Patent Document 1 to be described later, for example).
More specifically, the brake operation structure operatively connects the brake operating member and the brake pressing member so that the brake pressing member is rotated about the rotational axis line by an amount corresponding to a manual operation amount of the brake operating member. The group of friction plates are brought into frictional contact with each other at a level corresponding to the rotation amount of the brake pressing member about the rotational axis.
That is, the brake mechanism is set to generate braking power by the magnitude corresponding to the manual operation amount of the brake operating member. However, if the group of friction plates are abraded way or worn out, there is caused change in the relationship between the manual operation amount of the brake operating member and the level of frictional contact in the group of friction plates (that is, the magnitude of braking power generated by the brake mechanism). As a result, the brake mechanism may be incapable of generating sufficient braking power despite the fact that the brake operating member is manipulated by a predetermined amount.
The brake adjustment mechanism is provided in order to prevent such a defect.
However, the conventional brake operation structure had a problem of difficulty in operating the brake adjustment mechanism since the brake adjustment mechanism is disposed below the step of the working vehicle.
FIGS. 16A and 16B are a schematic side view and a schematic plan view of conventional brake operation structure, respectively.
As shown in FIGS. 16A and 16B, the conventional brake operation structure includes a brake operating member 1110, a brake operation shaft 1120, a brake actuating member 1130, a brake release biasing member (not shown), a brake control shaft 1160, a brake link member 1140, and a brake control atm 1150. The brake operating member 1110 can be manually operated. The brake operation shaft 1120 is rotated around its axis line in accordance with manual operation on the brake operating member 1110. The brake actuating member 1130 is supported by the brake operation shaft 1120 in a relatively non-rotatable manner with respect thereto. The brake release biasing member biases the brake actuating member 1130 toward a brake release position. The brake control shaft 1160 is supported by one of side walls of a transmission case 40 in a rotatable manner around its axis line in a state of straddling the one side wall so as to be extended inside and outside the transmission case 40 and being along the vehicle width direction. Axial rotation of the brake control shaft 1160 into the brake actuation direction causes the brake pressing member 63 to rotate about a rotational axis line 63X into the brake actuation direction. The brake link member 1140 has a first end operatively connected to the brake actuating member 1130 so as to be axially shifted in accordance with rotation of the brake actuating member 1130 about the brake operation shaft 1120. The brake control arm 1150 is connected to the brake control shaft 1160 in a relatively non-rotatable manner with respect thereto and is also connected with a second end of the brake link member 1140. A brake adjustment mechanism 1200 is inserted within the brake link member 1140 that is disposed below the step with being along a vehicle lengthwise direction.
In the conventional configuration described above, a worker is required to go underneath the step or to detach the step in order to reach the brake adjustment mechanism 1200, so that adjustment of the brake adjustment mechanism 1200 has been a troublesome job.
Patent Document 1 also discloses a brake/differential-lock operation structure applied to a working vehicle including a differential mechanism that switches between a differential state and a differential-lock state in accordance with a position of a differential-lock shaft in its axis line direction, and a friction-plate type brake mechanism that has group of friction plates and a brake pressing member and is configured so that, upon rotation of the brake pressing member about a rotational axis line into a brake actuation direction, the group of friction plates are brought into frictional contact with each other to operatively apply braking power to a travel power transmission path. The brake/differential-lock operation structure shifts the differential mechanism from the differential state into the differential-lock state in association with the brake operation of causing the brake mechanism to be shifted from the brake release state into the brake actuation state while allowing independent switch operation of the differential mechanism.
The brake/differential-lock operation structure is particularly useful in such a working vehicle in which the brake mechanism is disposed so as to apply braking power to a portion of the travel power transmission path that is positioned on an upstream side of the differential mechanism in the power transmission direction.
The brake/differential-lock operation structure operatively connects the brake operating member and the brake pressing member so that the brake pressing member is rotated about the rotational axis line by an amount corresponding to the manual operation amount on a brake operating member included in the working vehicle. Further, the group of friction plates are brought into frictional contact with each other at a level corresponding to the amount of rotation of the brake pressing member about the rotational axis line.
More specifically, the brake mechanism is set to generate braking power by the magnitude corresponding to the manual operation amount of the brake operating member. However, if the group of friction plates are abraded away, the relationship between the manual operation amount of the brake operating member and the level of frictional contact of the group of friction plates (that is, the magnitude of braking power generated by the brake mechanism) is changed. As a result, the brake mechanism may be incapable of generating sufficient braking power despite the fact that the brake operating member is manually operated by the predetermined amount.
In this regard, the conventional brake/differential-lock operation structure is provided with a brake adjustment mechanism.
The brake adjustment mechanism is capable of adjusting the position of the brake pressing member around the rotational axis line (that is, the initial position of the brake pressing member) in a case where the brake operating member is located at the brake release position.
The conventional brake/differential-lock operation structure with the brake adjustment mechanism is capable of maintaining appropriate relationship between the manual operation amount of the brake operating member and the level of frictional contact of the group of friction plates even in a case where the group of friction plates are abraded. On the other hand, readjustment of the brake adjustment mechanism changes an initial relative position between the brake operating member and a differential-lock pressing member, which is to be described later, thereby requiring readjustment of a link mechanism between the brake operating member and the differential-lock pressing member and/or readjustment of a link mechanism between the differential-lock operating member and the differential-lock pressing member.
FIGS. 16A and 16B are a pattern side view and a pattern plan view each showing the conventional brake/differential-lock operation structure.
As shown in FIGS. 16A and 16B, the conventional brake/differential-lock operation structure includes a brake operating member 1110, a brake operation shaft 1120, a brake actuating member 1130, a brake release biasing member (not shown), a brake control shaft 1160, a brake link member 1140, a brake control arm 1150, a differential-lock interlocking rod 1170, a first differential-lock pressing member 1180, a differential-lock operating member 1310, a differential biasing member (not shown), a differential-lock link member 1320, and a second differential-lock pressing member 1330. The brake operation shaft 1120 is rotated around its axis line in accordance with manual operation on the brake operating member 1110. The brake actuating member 1130 is supported by the brake operation shaft 1120 in a relatively non-rotatable manner with respect thereto. The brake release biasing member biases the brake actuating member 1130 toward a brake release position. The brake control shaft 1160 is rotatable about an axis line parallel to the rotational axis line 63X of the brake pressing member 63, and causes the brake pressing member 63 to rotate about the rotational axis line 63X into the brake actuation direction in accordance with rotation of the brake control shaft 1160 into the brake actuation direction. The brake link member 1140 has a first end operatively connected to the brake actuating member 1130 so as to be axially shifted in accordance with rotation of the brake actuating member 1130 about the brake operation shaft 1120. The brake control arm 1150 is connected to the brake control shaft 1160 in a relatively non-rotatable manner with respect thereto and has a first arm portion 1151 connected with a second end of the brake link member 1140 and a second arm portion 1152 provided separately from the first arm portion 1151. The differential-lock interlocking rod 1170 has a first end connected to the second arm portion 1152 so as to be axially shifted in accordance with rotation of the brake control arm 1150 about the brake control shaft 1160. The first differential-lock pressing member 1180 is rotatable about a first differential-lock control shaft 1180X that is substantially along the vertical direction, and has a connection portion 1181 connected to a second end of the differential-lock interlocking rod 1170 and a press portion 1182 axially pressing the differential-lock shaft 56. The first differential-lock pressing member 1180 is turned about the first differential-lock control shaft 1180X into the differential-lock direction via the differential-lock interlocking rod 1170 in association with movement of the brake control arm 1150 in a case where the brake operating member 1110 is shifted from the brake release position to the brake actuation position, so that the press portion 1182 presses the differential-lock shaft 56 toward the differential-lock position. The differential-lock operating member 1310 is supported in a rotatable manner about a differential-lock operation shaft 1310X. The differential biasing member biases the differential-lock operating member 1310 about the differential-lock operation shaft 1310X toward the differential position. The differential-lock link member 1320 has a first end operatively connected to the differential-lock operating member 1310 so as to be axially shifted in accordance with rotation of the differential-lock operating member 1310 about the differential-lock operation shaft 1310X. The second differential-lock pressing member 1330 is rotatable about a second differential-lock control shaft 1330X that is along the vertical direction, and has a connection portion 1331 operatively connected to a second end of the differential-lock link member 1320 and a press portion 1332 axially pressing the differential-lock shaft 56. The second differential-lock pressing member 1330 is turned about the second differential-lock control shaft 1330X into the differential-lock direction in accordance with movement of the differential-lock link member 1320 upon the differential-lock operating member 1310 being shifted from the differential position to the differential-lock position, so that the press portion 1332 presses the differential-lock shaft 56 toward the differential-lock position.
As shown in FIG. 16A, a brake adjustment mechanism 1200 is inserted within the brake link member 1140.
In the conventional configuration described above, readjustment of the relative position between the brake operating member 1110 and the brake control shaft 1160 by operating the brake adjustment mechanism 1200 also changes the relative position between the first differential-lock pressing member 1180 and the brake operating member 1110. Thus, in some cases, the first differential-lock pressing member 1180 unfavorably presses the differential-lock shaft 56 into the differential-lock direction despite the fact that the brake operating member 1110 is not manually operated.
The relative position among the brake operating member 1110, the brake control arm 1150, and the first differential-lock pressing member 1180 may be appropriately maintained by readjusting the initial position of the differential-lock shaft 56 after readjustment of the brake adjustment mechanism 1200. In this case, however, readjustment is also required to the differential-lock operation path connecting from the differential-lock operating member 1310 to the second differential-lock pressing member 1330.
Furthermore, sufficient consideration has not been made to the conventional brake/differential-lock operation structure in regard to the timing of switching the differential mechanism from the differential state into the differential-lock state in association with the manual operation on the brake operating member.
More specifically, the brake operation mechanism is configured such that the brake mechanism generates braking power by the magnitude corresponding to the manual operation amount of the brake operating member. In other words, the brake mechanism is shifted from a braking power release state into a maximum braking power generation state in accordance with the manual operation on the brake operating member from a braking power release position to a maximum braking power generation position.
Upon such brake operation, assume that the differential mechanism is shifted from the differential state into the differential-lock state after the brake mechanism is brought into the maximum braking power generation state. In this case, the maximum braking power is applied to the input portion of the differential mechanism in a state where a pair of drive axles are differentially driven. Accordingly, the working vehicle may turn in an unintended direction at the time when stopping the working vehicle by the braking power of the brake mechanism.
Particularly in a state where the pair of drive axles receive traveling loads unequal to each other as in traveling across an inclined road, upon stopping the working vehicle by braking power of the brake mechanism, the braking power may not be effectively applied to the drive axle receiving a smaller traveling load, thereby increasing the danger of causing the working vehicle to turn in an unintended direction.
To the contrary, considered is a case where the brake mechanism is configured to start generation of braking power after the differential mechanism is shifted from the differential state into the differential-lock state upon the brake operation. In this case, if the brake mechanism is actuated while the working vehicle is making a turn, braking power of the brake mechanism is applied to the travel power transmission path with the differential mechanism being in the differential-lock state. Therefore, one of driving wheels that is positioned on an outer side with turning center as a reference unfavorably slips.
Prior document 1: Japanese unexamined patent application publication No. 2007-055281